The five-time Ballon d'Or winner has been out of action since sustaining a calf injury in preseason, following his return to Camp Nou from the Copa America with Argentina, goal.com reported.
He was expected back on August 25 when Barcelona faced Real Betis at Camp Nou, but his scar reopened which extended his time away from the pitch for a couple of extra weeks.
The 32-year-old returned to full training on Monday morning and was included in Ernesto Valverde's 22-man squad for the trip to Westfalenstadion.
The Spanish champion has been drawn in Group F, alongside Dortmund, Inter and Slavia Prague.
Messi has not featured for Barca since a Copa del Rey final defeat against Valencia on May 25, with Valverde having to make do without a prized asset at the start of the season.
The Catalans are fifth in La Liga after four matches, posting wins over Betis and Valencia while also suffering an opening day defeat against Athletic Club and drawing with Osasuna.
Second-choice goalkeeper Neto was also included in Valverde's latest squad after a spell on the sidelines with a hand injury.
Teenage sensation Ansu Fati made the final cut after scoring his first goal at Camp Nou on Saturday.
The 16-year-old grabbed a goal and an assist on his maiden start for the club against Valencia, after becoming the youngest goalscorer in La Liga history with his strike at Osasuna last month.
Barcelona will be hoping it can improve on last season's semifinal showing in the Champions League, which saw eventual winner Liverpool spring a stunning second-leg comeback at Anfield.
Before the start of their latest campaign, Messi pledged Valverde's men will "fight for everything again,” insisting he had no regrets over how things turned out last term.